In substrate-manufacturing processes, deposition and etching of dielectrics and metal materials, coating and development of photoresists, asher process, etc are repeated a plurality of times to achieve delicate arrangement of patterning. However, although these processes including the etching or the asher process are performed, foreign substances still remain in substrates. Processes for removing these foreign substances include a cleaning process using deionized water or chemical.
Substrate-cleaning apparatuses performing the cleaning process are classified into a batch substrate cleaning apparatus and a single substrate cleaning apparatus. The batch substrate cleaning apparatus includes a chemical bath, a rinse bath, and a dry bath having sizes capable of processing 25 substrates or 50 substrates at once. The batch substrate cleaning apparatus removes foreign substances by immersing substrates in the respective baths for predetermined times. Such a batch substrate cleaning apparatus simultaneously cleans upper and lower portions of a substrate and processes a large amount of substrates simultaneously. However, as the diameters of substrates are increased, the sizes of baths are also increased, so as to increase the size of an apparatus and the amount of chemical. In addition, foreign substances detached from adjacent substrates are attached to substrates being cleaned in a chemical bath.
Recently, as the diameter of substrates is increased, the single substrate cleaning apparatus is widely used. In the single substrate cleaning apparatus, a substrate is fixed to a substrate chuck in a chamber having a small size adapted for processing a single substrate, then rotated by a motor, and then chemical or deionized water is provided to the substrate through a nozzle disposed over the substrate. The spin of the substrate spreads the chemical or the deionized water on the upper portion of the substrate, so as to remove foreign substances from the substrate. The single substrate cleaning apparatus has a smaller size than the batch substrate cleaning apparatus and achieves a uniform cleaning performance.
In general, the single substrate cleaning apparatus includes, from a side thereof, a loading/unloading unit, an index robot, a buffer unit, process chambers, and a main transfer robot. The index robot transfers substrates between the buffer unit and the loading/unloading unit, and the main transfer robot transfers substrates between the buffer unit and the process chambers. At the buffer unit, substrates to be cleaned wait to be inserted into the process chambers, or the substrates that have been cleaned wait to be transferred to the loading/unloading unit.
A transfer robot such as the index robot and the main transfer robot includes a plurality of arms, and a substrate is loaded on each of the arms. The respective arms move horizontally to take out or load substrates from or to storage such as front open unified pods (FOUPs) or the buffer unit.
FIG. 1 is a graph illustrating velocity variation of an arm in a typical transfer robot, and FIG. 2 is a graph illustrating velocity variation of two arms in the typical transfer robot when the arms simultaneously move.
Referring to FIG. 1, each of the arms is accelerated from a start time point ST when a horizontal movement starts, to a first time point T1 when the arm reaches a maximum velocity UV, then the maximum velocity UV is kept from the first time point T1 to a second time point T2 when the arm is gradually decelerated. That is, the arm is in uniform motion at the maximum velocity UV from the first time point T1 to the second time point T2. The arm of the transfer robot is gradually decelerated from the second time point T2 to a target time point ET when the horizontal movement is finished, that is, to the point ET when the arm stops in a storage device.
As such, a horizontal movement profile of the arm in the transfer robot sequentially includes an acceleration division where the velocity is gradually increased, a constant velocity division where the arm moves in uniform motion, and a deceleration division where the velocity is gradually decreased.
Such a transfer robot's arms are driven independently, and thus the respective arms have separate horizontal driving shafts, and assembling tolerance occurs between the arms. Accordingly, when driving at least two arms together, velocities of the respective arms are different, so that time points when the respective arms arrive at target points are different.
Referring to FIG. 2, when the two arms A1 and A2 are moved horizontally together, the start time points ST when the two arms A1 and A2 start to move horizontally are the same, and the time points T1 when the two arms A1 and A2 reach the maximum velocity UV are the same. However, since the time point T2 when the first one A1 of the two arms A1 and A2 is decelerated is different from a time point T3 when the second one A2 is decelerated, time points ET1 and ET2 when the two arms arrive at target points are different.
As such, when simultaneously driving the arms of the transfer robot, the time points when the arms arrive at the target point are different, and thus it is difficult to simultaneously take out a plurality of substrates from the storage device.